RK-55

The Novator RK-55 Relief (Russian: РК-55 Рельеф 'Relief'; NATO: SSC-X-4 'Slingshot'; GRAU: 3K12) is a Soviet land-based/submarine-launched cruise missile with a nuclear warhead. It was about to enter service in 1987, when such weapons were banned under the Intermediate-Range Nuclear Forces Treaty. A version launched from submarine torpedo tubes, the S-10 Granat (SS-N-21 'Sampson'; GRAU: 3K10), has apparently been converted to carry conventional warheads and continues in service to this day.[3] The Russian Federation was reported to have deployed the derivative SS-CX-7/SS-CX-8 systems on February 14, 2017.

The RK-55 is very similar to the air-launched Kh-55 (AS-15 'Kent') but the Kh-55 has a drop-down turbofan engine[4] and was designed by MKB Raduga. Both have formed the basis of post-Cold-War missiles, in particular the Sizzler which has a supersonic approach phase.[5]

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In the late 1960s, the "Ekho" study conducted by the GosNIIAS institute concluded that it would be more effective to deploy lots of small, subsonic cruise missiles than the much more expensive supersonic missiles then in favour.[6] In 1971 Raduga began working on the air-launched Kh-55, which first flew in 1976.[4] That same year, RK-55 first flew.[5]NPO Novator would work on the submarine- and ground-launched versions. In 1993 Novator exhibited the Sizzler series weapons, which appears to be based on the RK-55.[5] It is a two-stage design, which goes supersonic during its final approach to the target.

The four Grusha-class (Yankee Notch) submarines deployed in 1988[2] is a design of particular note, replacing the missile compartment of a Yankee class SSBN with additional torpedo tubes for 35-40 land attack cruise missiles. They were probably nuclear-tipped S-10s during the Cold War, and then converted to use conventional warheads [8] after the START I treaty restricted sub-launched nuclear cruise missiles. The US Navy has done the same on a grander scale with the SSGN conversions of four Ohio-class submarines. It has been suggested that S-10's could in future be fitted to converted Delta class submarines, or to surface ships, but these have not been confirmed.[5]

In early 2017, unverified reports emerged that Russia was violating the INF through the deployment of the 9M728 (SS-CX-7) and 9M729[13] (SS-CX-8) missiles as part of the Iskander missile system. These are widely reported as variants of the earlier SS-C-4. According to U.S officials, two missile battalions equipped in SSC-8 were deployed as of 14 February 2017 in violation of the treaty.[11][14][15] Each battalion consists of 4 launchers, each launcher supplied with six nuclear-tipped cruise missiles. One battalion is allegedly located at Kapustin Yar near Volgograd; the other's location is unknown at this time. The German newspaper FAZ argues in February 2019 that in addition to two known locations where missiles and battalions are stationed - at a launch pad at Kapoustin Iar, in southern Russia, and Yekaterinburg - there would be two other places equipped with these missiles. : Mozdok in North Ossetia and Shuya near Moscow. Each of the four battalions would have four wheeled launchers, each carrying four missiles, adds the German media. This brings to 64 SSC-8 missiles in Russia's possession, which can be armed with conventional or nuclear warheads. This type of missile has a range of 2,350 kilometers. With a conventional warhead of 500 kilos, the range is 2,000 kilometers.[16]